Abstract

Automatic control, particularly the application of feedback, has been fundamental to the development of automation. Its origins lie in the level control, water clocks, and pneumatics / hydraulics of the ancient world. From the 17th century onwards, systems were designed for temperature control, the mechanical control of mills, and the regulation of steam engines. During the 19th century it became increasingly clear that feedback systems were prone to instability. A stability criterion was derived independently towards the end of the century by Routh in England and Hurwitz in Switzerland. The 19th century, too, saw the development of servomechanisms, first for ship steering and later for stabilization and autopilots. The invention of aircraft added (literally) a new dimension to the problem. Minorsky’s theoretical analysis of ship control in the 1920s clarified the nature of three-term control, also being used for process applications by the 1930s. Based on servo and communications engineering developments of the 1930s, and driven by the need for high-performance gun control systems, the coherent body of theory known as ‘classical control’ emerged during and just after WW2 in the US, UK and elsewhere, as did cybernetics ideas. Meanwhile, an alternative approach to dynamic modelling had been developed in the USSR based on the approaches of Poincaré and Lyapunov. Information was gradually disseminated, and ‘state-space’ or ‘modern control’ techniques, fuelled by Cold War demands for missile control systems, rapidly developed in both East and West. The immediate post-war period was marked by great claims for automation, but also great fears, while the digital computer opened new possibilities for automatic control.